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Periodic Table and Valence Electrons

Periodic Table Organization

  • Elements are organized into:
    • Groups (columns): Indicate the number of valence electrons.
    • Periods (rows): Indicate the number of electron shells.

Metals

  • General Properties: Shiny (Luster), easily pulled into wires (Ductility), easily hammered into thin sheets (Malleability), good conductors of electricity and thermal energy.
  • Metallic Property Trends: Increase from right to left across a period; increase from top to bottom within a group.
  • Group 1: Alkali Metals:
    • Elements: Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), Francium (Fr).
    • Very reactive, silver in color, very soft, low density.
  • Group 2: Alkali Earth Metals:
    • Elements: Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), Radium (Ra).
    • Not as reactive as Alkali Metals, occur naturally only as compounds, low density (but greater than alkali metals), silver in color.
  • Groups 3-12: Transition Metals:
    • Possess higher density, greater strength, and higher melting points.
    • Less reactive than Alkali and Alkali Earth Metals.

Non-metals

  • General Properties: Generally poor conductors (good insulators).
  • Group 17: Halogens: React with metals to form salts.
  • Group 18: Noble Gases:
    • Elements: Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn).
    • React with other elements only under special conditions.
  • Other: Hydrogen is the most common element in the universe.

Metalloids

  • Properties: Elements that exhibit physical and chemical properties of both metals and non-metals.
  • Examples: Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), Polonium (Po), Astatine (At).

Valence Electrons

  • Definition: Electrons located in the outermost shell of an atom.
  • Function: These electrons are responsible for forming bonds with other atoms.
  • Determination:
    • Groups: Tell the number of valence electrons for elements in that group (e.g., Group 1 has 1, Group 17 has 7).
    • Periods: Indicate the total number of electron shells an element has.
  • Examples:
    • Calcium: 4 shells, 2 valence electrons.
    • Nitrogen: 2 shells, 5 valence electrons.
    • Chlorine: 3 shells, 7 valence electrons.
    • Lead: 6 shells, 4 valence electrons.
    • Oganesson: 7 shells, 8 valence electrons.
  • Reactivity Principle: Halogens (with 7 valence electrons) react aggressively with Alkali Metals (with 1 valence electron) because 1 + 7 = 8, satisfying the octet rule for stability.